Variable aperture diaphragms for optical lens systems have been the subject matter of many prior art disclosures and apparatus; however using a variable aperture devise of the prior art in telescopic gunsights has been impractical and overly expensive, especially considering the problem of sealing the externally actuated adjustment mechanism of the unit against escape of the nitrogen gas contained in the scope to prevent fogging of the lenses. The shock forces to which gun scopes are usually subjected also mitigate against use of the prior art adjustable aperture devices in gun scopes.
The prior art concerning optical systems and adjustable apertures is voluminous, but the prior United States patents which are known to applicants and which deal with this type of device in the setting of the present invention are Nos.: 1,353,151; 2,371,744; 3,981,565; ,3,997,906; 4,047,807; and 4,392,723, none of which disclose apparatus which is anticipatory of the present invention.
It is therefore the principal object of the present invention to provide an externally actuated adjustable optical aperture device for use especially in telescopic gunsights.
Another and incidental object of the invention is to provide a device in an optically augmented gunsight which can control the amount of light reaching the eyepiece lenses so that in bright daylight, when the amount of light coming through the objective lens hinders the optical performance of scope, the light may be reduced so that the image of the target is sharper and more clearly defined; and conversely, when, in twilight conditions and maximum light is required to visualize the target, the aperture may be adjusted to admit all of the light passing through the objective lens.
A further object of the invention is to provide a means of increasing the depth of the focus field of a scope and decreasing parallax by elimination of the edge rays of the total bundle of light rays passing through the objective lens system.
Another object of the invention is to provide a simple and inexpensive externally actuated adjustment mechanism which may be sealed so as to retain the nitrogen gas encapsulated within the scope.
A still further object of the invention is to provide a series of different mechanisms for varying the light admitted to the eyepiece lenses, but all with a generically simple external adjustment mechanism.
Other and still further objects, features and advantages of the present invention will become apparent upon a reading of the detailed description of the various embodiments of the invention, taken in conjunction with the accompanying drawings in which: